The invention relates to a connectable bucket tappet for a valve drive of an internal combustion engine, having a ring shaped section which has a skirt for oscillatory mounting in a holder of an internal combustion engine and, in its bore, accommodates a circular section such that it can move axially, it being possible for the two sections to be coupled to each other in at least one axial displacement position in relation to each other via at least one slider which can be displaced radially or in the manner of a secant and which runs in the circular section in the uncoupled state, holders for the slider being provided in the region of bases of the sections and an outer surface of the circular section being enclosed by at least one compression spring which, at one end, acts against the base of the ring shaped section and, and the other end, acts against a support of the circular section which is remote from the base.
A bucket tappet of this type is previously known from U.S. Pat. No. 5,651,335. In this, two sliders are arranged in the vicinity of the base of the circular section and, for the coupling case, can be displaced radially outward into a corresponding holder of a ring shaped section. The disadvantage in the case of the generic tappet is that, in particular, its ring shaped section is relatively complicated to produce. This is based on the fact that its holders are connected thereto in one piece. The relatively massive transverse web present in the ring shaped section in order to form the holders makes fabrication, in particular chip-free fabrication, of the ring shaped section relatively expensive. Furthermore, it must be noted that only a relatively short compression spring can be used as a lost-motion spring because of the transverse webs.
It is therefore an object of the invention to provide a connectable tappet of the aforementioned type in which the cited disadvantages are eliminated with simple means.
According to the invention, this object is achieved by the holder of the ring shaped section being formed as a separate, sleeve-like component, which extends only over a small part of an annular width of the ring shaped section and runs with its inner edge immediately in front of the outer surface of the circular section, the component being enclosed at least sectionally by the compression spring radially on the outside and in the axial direction of the bucket tappet.
By means of these aforementioned simple measures, it is possible to dispense with the transverse web disadvantageously present in the prior art. Thus, production of the ring shaped section of the tappet is considerably less complicated and therefore cheaper than in the prior art. At the same time, the installation space for the compression spring as a lost-motion spring is increased. As a result if necessary, the tappet height can be reduced or a greater relative stroke of the sections in relation to one another can be produced. Precisely as a result of these measures according to the invention, relatively simple chip-free fabrication for the ring shaped section is suggested. Although, radial webs on the base side in the ring shaped section are not dispensed with completely, these are formed merely like weak ribs and are used to support an annular part of the compression spring as a lost-motion spring and, if appropriate, as a subdivision for two separate hydraulic fluid chambers.
Preferably, the intention is to apply only one slider arranged in the circular section. However, two sliders are also conceivable, which can be displaced radially outward for a coupling purpose. In this case, two diametrically opposite, sleeve-like components then have to be applied in the ring shaped section.
Thought is given in particular to a piston or pin as slider. However, a large number of further coupling elements, such as pawls, balls, wedges and the like, are also conceivable.
The sleeve-like component has only a low depth and is preferably produced from a sheet metal material. Here, a simple deep-drawing method is suggested for its production. If appropriate, a plastic or other lightweight component can also be used.
The sleeve-like component has at least one vent opening, which will not be explained in more detail, or a vent duct, in order to avoid the undesired build-up of an air cushion during the coupling operation.
According to a further feature, the annular extension from the inner edge of the base of the ring shaped section is used firstly for excellent guidance of the circular section in the ring shaped section. Secondly, it has a radial opening for the simple fixing of the sleeve-like component.
Furthermore, it is a further feature to produce a simple antirotation safeguard for the sections in relation to one another by an inner edge of the sleeve-like component, which communicates with a flat on the outer surface of the circular section. Of course, those skilled in the art will discover still further antirotation measures of a form-fitting type.
The fact that the slider is loaded in a displacement direction, preferably in the coupling direction, via at least one helical spring enclosing the latter, means that the holder for the slider in the circular section needs have only a relatively short length. Otherwise, the helical spring would have to be applied to the end of the slider. However, it is also conceivable to load the slider in the coupling direction via compression spring force and to displace it in the uncoupling direction via hydraulic means. If appropriate, other displacement means such as electromagnetic, magnetic and the like can also be used.
The radial webs originating from the base of the ring shaped section are used, as mentioned, for the contact of an annular part. Thus, two segment-like spaces for hydraulic fluid can be implemented, at least one chamber being used for the feed line of the hydraulic fluid in front of one end of the slider. The further chamber can be connected hydraulically to the first-named chamber. However, it can also be used as a supply chamber for the supply of an optionally applied hydraulic play compensating element in the circular section. If appropriate, the slider or the hydraulic element can be supplied virtually directly with hydraulic fluid from the cylinder head via a bore in the skirt.